It has long been known that the application of heat or cold to an injury can influence blood circulation at an injured site, decrease swelling, and increase the comfort of the patient. In the past, such treatment included the use of hot water bottles and ice packs. More recently, however, such treatment has evolved into a therapy using a fluid, such as water, as a thermal transfer media. The fluid is heated or cooled by appropriate means within a housing, and pumped through a conduit, to a pad, which is in contact to the injured portion of the user. Sometimes during the course of using a thermal therapy device, the flow of the fluid will be blocked. Flow blockage occurs, for example, when the pad becomes tangled in the bedclothes or if the patient is improperly positioned on the pad. It is typical for flow blockage to be a problem at the fluid inlet to the pad.
While it has been proposed to solve flow problems through the use of a higher pressure pump, this also can be a problem. A higher pressure pump may cause problems such as ballooning of the pad or rupture of the pad membrane. Moreover, it is not practically possible to increase the pressure to overcome crimping or flow restrictions and provide for continuity of flow. These problems result from the characteristics of the pad material, for example, it is desirable that the pad material is thin in order to maximize heat transfer characteristics. In addition, the pad material should be flexible in order to maximize the contact with the patient through a variety of positions. Notwithstanding the fact that the membrane is thin and flexible, it is best to provide for low probability of leakage for reasons of patient safety. Therefore, the fluid pressure in the pad should be below 20 psi, and most preferably below about 10 psi.
It is desirable to combine thermal therapy with other therapies, such as continuous passive motion which involves the passive flexion and extension of an injured joint. While a combination of these therapies may be of great medical benefit to the patient, there are certain mechanical difficulties in combining these therapies. Most notably, the prior art thermal transfer pads present problems with blockage to fluid flow. Obstructions to fluid flow are a problem if, for example, a thermal transfer pad is applied when the patient is bandaged in the operating room, and in particular if the patient is subsequently subjected to CPM therapy. The prior art pads have had a tendency to crimp at the joint between the fluid transfer conduit and the pad. One prior art solution to this problem, is an alternative circuit from the inlet conduit to the outlet conduit of the pad. While this solution maintains the fluid flow through the housing, it obviates the therapy, since it inhibits the application of heat or cold to the patient through the pad.
It is therefore an object of the present invention to provide a thermal therapy pad which is suitable for use in the application of thermal therapy, in conjunction with continuous passive motion therapy. This pad is unique in that it has a soft flexible inlet reinforcement. This inlet reinforcement specifically consists of a soft flexible fluid inlet having a flow opening with an increased area through which the fluid diffuses into the pad. It is advantageous if the fluid outlet is similarly reinforced.
The pad of the present invention has increased reliability inhibiting flow obstruction, and the reliability results from a increased area of diffusion in the pad inlet as well as from inlet reinforcement.
In a preferred embodiment of the present invention, the increased area of diffusion is provided by a double conduit construction. A soft flexible inner flow surface, or conduit, is provided, which assures that the inlet remains an open conduit by providing alternate escape paths for the transfer fluid. In a most preferred embodiment, the inner flow surface is provided by a spiral cut inlet reinforcement which extends from the inlet conduit into the body of the thermal transfer pad.